1. Field of the Invention
The present invention relates to a device mounting structure and a device mounting method.
2. Description of the Related Art
In a mounting method for a power device (hereinafter, referred to as a device) for the RF (Radio Frequency), a bonding method, which is used to bond a heat-radiating surface of a device main part to a heat-radiating plate, has become more important along with the increasing high power output. To assure a steady bonding area of the device, such a method is currently implemented that the device is soldered to the heat-radiating plate. In the method, it is necessary to fix an RF board and the heat-radiating plate to mount the device to the RF board and the heat-radiating plate at the same time.
While a soldering method or a resin method is available as a fixing method, the cost is high. It is hard to fix a position for mounting the device when soldering the device, and a lead of the device and a wiring pattern are frequently different to each other in the height. Thus, a manual production process is increased to mount such a device, and the process cost for the heat-radiating plate is also increased, so that a process method for the heat-radiating plate and the PWB has been studied.
The related technique corresponds to Patent documents 1 to 6:    Patent document 1: Japanese Patent Laid Open Publication No. 2003-188461;    Patent document 2: Japanese Patent Laid Open Publication No. 2003-289118;    Patent document 3: Japanese Patent Laid Open Publication No. 7-14949;    Patent document 4: Japanese Patent Laid Open Publication No. 8-264910;    Patent document 5: Japanese Patent Laid Open Publication No. 9-139450; and    Patent document 6: Japanese Patent Laid Open Publication No. 9-232715.
The invention described in the Patent document 1 corresponds to a semiconductor laser driving apparatus provided with a print board in which a semiconductor laser is mounted. This semiconductor laser is mounted as a unity on the heat-radiating plate with an enough area for covering a circuit that is mounted on the print board, and is related to noise generation. This semiconductor laser is mounted on the print board so that the heat-radiating plate covers the circuit related to the noise generation on the printed board.
According to this semiconductor laser driving apparatus, it is possible to cause the heat-radiating plate to function as not only a heat-radiating component but also a shield for an emission noise.
In the Patent document 2, in such a mounting structure that a heat sink is provided in a rear side of a board, a plate containing a bottom side of a circuit part with the board, or such a plate and at least one metal plate are provided between the board and the heat sink so that the bottom side of the circuit part arranged on a surface of the board is contacted to the heat sink. In this mounting structure, the bottom part of the circuit part is contained by the plate, or the plate and the metal plate, and the bottom part of the circuit part is directly or indirectly connected to the heat sink.
According to this mounting structure, it is possible to transfer the heat generated in the circuit part from the bottom side to the heat sink, and to radiate the transferred heat, and it is possible to apply the heat sink, in which a surface is flat, and a type is one, regardless of the size of the bottom side of the circuit part.
The invention described in the Patent document 3 corresponds to a semiconductor module in which a peripheral circuit of a semiconductor element such as a high-frequency transistor is formed on a ceramic board, and the ceramic board is soldered to the heat-radiating plate. In this semiconductor module, the ceramic board includes a through hole in an area for mounting the semiconductor element such as the high-frequency transistor with a large amount of generated heat. The heat-radiating plate includes a projection part in a position of the heat-radiating plate, which corresponds to an area for mounting the semiconductor element. The semiconductor element such as the high-frequency transistor is directly bonded to the projection part of the heat-radiating plate through the through hole of the ceramic board.
According to this semiconductor module, a convex part is provided in the heat-radiating plate, the transistor is directly mounted to the convex part through the through hole of the ceramic board, so that it is possible to improve the heat-radiating effect and the quality.
The invention described in the Patent document 4 corresponds to a production method, configured with the following processes (a) to (d), for producing the print wired board with the heat-radiating plate. (a) A process in which release paper, to which adhesive is applied, is bonded, through this adhesive, to another side of an insulation plate of the print wired board with a wiring pattern on one side of the insulation plate. (b) A process in which the through hole is formed at a high power part mounting position of the print wired board to which the release paper is bonded. (c) A process for peeling the release paper. (d) A process for bonding, with the adhesive, the heat-radiating plate to the insulation plate.
According to this production method, a process is not necessary, in which the convex part is conventionally formed in the metal heat-radiating plate according to the position of the through hole formed in the print wired board, and an easy production method and an easy mounting method can be realized. In addition, the metal heat-radiating plate can be provided, with the both side bonding means, in the print wired board without being positioned to the through hole provided for mounting a high power part package.
The invention described in the Patent document 5 corresponds to a fixing method for fixing the heat sink for radiating the heat generated in a semiconductor integrated apparatus. In this fixing method, the heat sink, in which a screw hole is formed at a predetermined position, is arranged on the semiconductor integrated apparatus that is soldered to be arranged on the board, and is passed, from a back side of the board, through a compression coil with a predetermined spring force and the through hole provided in the board. A screw component is screwed in the screw hole of the heat sink, and by the spring force of the compression coil biasing the screw component in a direction of escaping from the board, the heat sink is closely fixed on the upper side of the semiconductor integrated apparatus.
According to this fixing method for fixing the heat sink, the heat sink is, by the spring force of the compression coil, flexibly and closely fixed on the upper side of the semiconductor integrated apparatus. Thereby, it is possible to avoid such a condition that the stress is applied to the semiconductor integrated apparatus, and to prevent a disadvantage such as a solder crack and a fold of a lead pin. In addition, the productivity is also more excellent than the conventional bonding method.
The invention described in the Patent document 6 corresponds to a mounting method for mounting a power transistor when a high frequency power amplifying module is produced. In this mounting method, a circuit board is mounted on a module heat-radiating plate to which cream solder is applied, and the bear chip-like power transistor with the heat-radiating plate is dropped down in a dropping-down hole provided in the circuit board, and is reflow-soldered. In this mounting method, when the cream solder is applied to the module heat-radiating plate, a not-applied part is provided in a part of a part corresponding to the dropping-down hole of the circuit board.
According to this mounting method for mounting the power transistor, a direction of a gate G to a drain D of the power transistor is stabilized at a certain position in the dropping-down hole, thereby, it is possible to stabilize the amplification characteristic, and to largely reduce adjusting work for a circuit constant.
However, in the techniques described in the above Patent documents 1 to 6, when the reflow process is applied to the wired board, the short circuit may be induced between a device lead part and a device ground part of the device.